Mozilla is unhappy because the use of browser engines other than WebKit will be restricted to the EU, forcing them to develop two different apps.
For an independent browser like Firefox, managing two browsers is not easy, so it can be forgiven that this could be seen as almost harassment.
Also, the fact that the use of browser engines other than WebKit is limited to iOS means that the use of WebKit is still forced on iPadOS, which also increases the effort for Mozilla.
I know that, but why did you bring it up in order to contrast it with Mozilla’s consumer base? Do you mean to say that Google is the actual paying customer?
It seems like such a bizarre thing to bring up at all.